EMPLOYEE DOING OWN CLIENTS TAX RETURNS AT WORK - ADVICE REQUIRED

I have recently found evidence showing that one of our employees has been filing tax returns for his own clients whilst at work. We have verbally warned him in 2007 about this. We are a small practice who would need to replace this person straight away and are not sure how easy it would be to do this given the current climate

Just wondered if anyone else has had any experience in dealing with this sort of situation. He has been with us for over 20 years and has no written contract of employment. He does work alongside a sub contractor and we feel that if confronted he would say it was them.